The typical asking rate per listing is in the $30's per square foot per year. The National City region is experiencing a an increase in rates. In the last 3 months, the median rate increased $31 per sqft per year.
Compared to the rest of the San Diego market, the National City region has less expensive rates, so you should have no trouble finding a great deal in this depreciated submarket.
In the last 90 days, 5 listings have come on the market, which means spaces are probably leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 300% of the available space in the National City are subleases, so you might be able to snag a great spot on a short term. There aren't many listings below 2,000 square feet available, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,010 sqft. Most buildings in this region are close to 2 stories. Most buildings in this region were built in 1974 and are Class B.